Microbial communities found on the Boston subway system are largely composed of normal human skin commensals and are incapable of causing disease, according to data published recently in mSystems.
Curtis Huttenhower, PhD, an associate professor of computational biology and bioinformatics at the Harvard T.H. Chan School of Public Health, and colleagues collected 73 samples from train cars and stations in the Boston transit system, known as the T, on 3 dates in 2013.
Samples from the train cars were collected from 6 surface types, including hanging grips, horizontal and vertical metal poles, seats, seat backs, and the walls. Researchers also collected samples from the touch screens and sides of the ticketing machines at the stations. They used 16S amplicon and shotgun metagenomic sequencing of the samples to profile the microbial communities found on these surfaces.
The researchers noted that while the microbial community structure was the transit surface type, there was little variation between geographically distinct train lines. Overall, the biomass yields were highest among the hanging grips (141.83 ± 92.68 ng/µl) followed by seats (128.1429 ± 49.955 ng/µl) and touch screens (120.47 ± 73.68 ng/µl).
All of the surfaces that the researchers tested were covered with normal human skin microbes, including Propionibacterium, Corynebacterium, Staphylococcus, and Streptococcus. They also found low levels of gut microbes from the Veillonella and Prevotella families.
Shotgun metagenomics also identified additional viral and eukaryotic microbes, including Propionibacterium phage and Malassezia globosa. Propionate production and porphyrin synthesis were enriched on the hanging grips, and electron transport chain components for aerobic respiration were enriched on the touch screens and seats. Overall, the subway was not substantially populated with antimicrobial resistance and virulence genes.
“We were surprised by how normal a lot of the samples looked,” Dr Huttenhower stated in a press release. “Even when we looked closely, there was nothing unusual or dangerous about the microbes we found. It shows that, in the absence of something like flu season, all of the germs you run into, even in a crowded environment like the T, are normal.”
Hsu T, Joice R, Vallarino J, et al. Urban Transit System Microbial Communities Differ by Surface Type and Interaction with Humans and the Environment. mSystems. 2016; doi: 10.1128/mSystems.00018-16.